There is a growing need for efficient, high quality and low cost high-protein food sources with acceptable taste, flavor and/or aroma profiles. However, it has proven difficult to achieve such products, particularly with low cost vegetarian protein sources.
Previous work discloses culturing of fungi using low amounts of protein in the culture media. U.S. Pat. No. 2,693,665 discusses the submerged culturing of Agaricus campestris grown in citrus juice, pear juice, asparagus juice, “organic material”, a carbohydrate, a nitrogen source, and any combination of these materials optionally supplemented with urea and/or various ammonium salts.
U.S. Pat. No. 2,761,246 teaches a method for the production of submerged Morchella esculenta, and more broadly Helvellaceae mycelium for the purposes of creating a human foodstuff. The publication discusses the use of various molasses solutions as media supplemented with ammonium salts and the inclusion of calcium carbonate or calcium sulfate as nucleation sites for hyphal spheres to increase biomass yield 30 fold. In general, the patent teaches the art of growing submerged mycelium on a carbohydrate source “such as many of the monosaccharides, or some of the disaccharides or their hydrolysates” and a nitrogen source “such as ammonium salts or amino acids or any kind of protein hydrolysate”. The culture propagation motif includes three separate cultures and an intermittent filtering step.
U.S. Pat. No. 2,928,210 discloses a method to produce mushroom mycelium from sulfite liquor waste supplemented with organic and inorganic salts, presenting the idea as an efficient way to prevent sulfite liquor pollution. Culture propagation does require that the mycelium be washed to remove residual liquor, taught as a necessary step to make the product human food grade. This introduces the disadvantage of washing away exocellular solids that would otherwise greatly contribute to yield. This also introduces a new waste stream that will presents the same problems the publication is trying to solve.
U.S. Pat. No. 3,086,320 discloses a method to improve the flavor of submerged mycelium of M. ‘esculema’, Helvella gigas, Coprinus comatus, and A. campestris by growing the strains in a media comprising milk. The patent claims the major issue of edible mycelium is that “the mycelium, while similar in flavor to the natural sporophore, falls short in matching it in intensity and kind.” The patent teaches the use of 1 to 50% (v/v) natural skim milk to media, or 0.33 to 16.66% condensed natural skim milk with nonfat dry milk solids in an amount of about 0.03 to 1.66% (w/w) to the condensed natural skim milk if the condensed milk is being substituted for the non-condensed. If using natural skim milk, milk protein hydrolysate can be used in an amount of about 5% (w/w). The patent recommends using skim milk in an amount between 5-10% (v/v) to media. Mycelium flavor is said to improve with higher concentrations of milk.
U.S. Pat. No. 4,071,973 discloses culturing conditions for Basidiomycetes. The patent teaches to inoculate media with “a body of a fungus” and supply “inorganic nutrient salts for nitrogen, phosphate and potassium,” mixed with sucrose at 50-70 g/L and supplemented with fine powder of “crushed sugarcane, sugarcane bagasse, pine tree-tissue and wheat bran” at 0.2-15 g/L. Oxygen is controlled at 30-90% (v/v) to the media and the vessel is pressurized at 0.12-0.5 MPa (17.4 to 72.5 psi) with oxygen supplied at 0.1 to 1.0 L/minute. Salts used include ammonium nitrate, sodium phosphate, magnesium sulfate heptahydrate, iron (II) sulfate heptahydrate and dipotassium hydrogen phosphate. Air pressure cycles are controlled with a pressure regulator. The patent states that cell growth enhancement through elevated oxygen levels is unexpected.
There is therefore a need for efficient, high quality and low cost high-protein food sources with acceptable taste, flavor and/or aroma profiles, and for a process that enables the myceliation of highly proteinaceous media, specifically media that are greater than 50% protein on a dry weight basis.